tree-wide: Remove dead code

This code seems to not be used anywhere at all, so let's drop it.

Follow up for ba8d00e859
Follow up for 85686b37b0
Follow up for aff853f8ea
Follow up for 36dad381a2

src/basic/ether-addr-util.h

@@ -72,7 +72,6 @@ extern const struct hash_ops hw_addr_hash_ops_free;
 
 #define ETHER_ADDR_TO_STRING_MAX (3*6)
 char* ether_addr_to_string(const struct ether_addr *addr, char buffer[ETHER_ADDR_TO_STRING_MAX]);
-int ether_addr_to_string_alloc(const struct ether_addr *addr, char **ret);
 /* Use only as function argument, never stand-alone! */
 #define ETHER_ADDR_TO_STR(addr) ether_addr_to_string((addr), (char[ETHER_ADDR_TO_STRING_MAX]){})